The present invention relates to a microwave reflector antenna and, more specifically, to a microwave reflector antenna for attachment to an aircraft.
Microwave reflector antennas can be used in airborne applications. For example, microwave reflector antennas can be used on an aircraft to allow the aircraft to communicate with other parties. When the microwave reflector antenna is used on an aircraft, the microwave reflector antenna may be positioned on the crown of the exterior of the aircraft. The positioning of the microwave reflector antenna on the exterior of the aircraft increases the drag of the aircraft as it travels through the atmosphere and exposes the microwave reflector antenna to the harsh environments that the aircraft is exposed to. Therefore, the microwave reflector antennas are typically covered by a radome which completely covers the microwave reflector antenna and reduces the drag caused by positioning the microwave reflector antenna on the exterior of the aircraft.
Because the cost of the radome is proportional to the size of the radome, any reduction in the height of the radome will result in a cost savings. Additionally, decreasing the size of the radome will also decrease the drag caused by the radome on the aircraft. Therefore, it is desirable to reduce the height of the microwave reflector antenna so that the height of the radome can also be reduced.
Additionally, RF components such as orthomode transducers (OMT""s), solid state power amplifiers (SSPA""s), and low noise amplifiers (LNA""s) are often used in reflector antennas. These components typically are remotely located from the antenna. However, if the RF components are remotely located from the antenna, the waveguide which interconnects the antenna to the RF components will introduce higher RF losses. RF losses occur because the RF components are typically located by a distance of many feet away from the antenna and the interconnecting waveguide is too long. Waveguides are also difficult to fabricate, costly, heavy, and difficult to install into aircraft.
Furthermore, the use of a waveguide to connect the antenna to the remotely located RF components requires a waveguide azimuth rotary joint. A rotary joint is used to interconnect the movable antenna to the stationary aircraft fuselage. A waveguide rotary joint is considerably larger and more costly than a coaxial rotary joint. As a result, antennas that use a waveguide rotary joint are larger and increase drag.
Therefore, a microwave reflector antenna that utilizes RF components mounted directly onto the antenna is needed so the antenna has a minimum height, minimum RF losses, and so the antenna may utilize a coaxial rotary joint. Also, if the antenna has a minimum height, the radome necessary to cover the antenna will also be of a minimum size which will reduce the cost to build and operate a microwave antenna, reduce aerodynamic drag, and reduce the swept volume of the microwave antenna.
The present invention provides a microwave antenna for an aircraft including a reflector element with a front surface and a rear surface. A horn is mounted to the front surface of the reflector element and an orthomode transducer is mounted to the rear surface of the reflector element. The orthomode transducer is coupled to the horn. Solid state power amplifiers that amplify a microwave signal to be transmitted and low noise amplifiers that amplify a received microwave signal are coupled to the orthomode transducer. The solid state amplifiers and the low noise amplifiers are also located on the rear surface of the reflector element.
The inherent advantage of this design is that it permits the use of smaller RF components such as the LNA""s and the SSPA""s. These lower wattage units have less concentrated heat to dissipate, can be readily mounted directly onto the antenna and result in the lowest possible RF losses.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.